The growing public concern for the environment has lead to a corresponding rise in governmental regulations. One area that has received particular attention, and thus onerous regulations for industry, is the protection of soil and groundwater. Due to the great potential for leaching of substances into the water table and impacting on municipal water supplies, the regulations have become stringent and far-reaching. In some areas, for example, all commercial metal underground storage tanks have had to be replaced with more durable fiberglass tanks equipped with integral leak detection systems.
In the transportation of potentially dangerous substances, such as dry, bulk chemicals, liquid waste and petroleum products, it is imperative to prevent the materials from entering the soil. Once in the soil, it is both difficult and expensive to remove them. For such wet and dry materials, the chief mode of transport is tanker and container trucks. Whenever material is loaded in or unloaded from a container truck, there is always the potential for some material to be spilled. This may be a small amount, such as the residual liquid that may drip when a hose is disconnected. However, given the numerous transfers per day that take place, a significant amount of material may accumulate in the areas of the transfers. In an accident, large amounts of material may be spilled. Without any protection, these materials will end up on the ground, soaking into the soil and eventually into the water table.
To prevent this, regulations in many areas mandate that such truck transfers take place on transfer pads. These pads usually consist of a liquid-impervious concrete base that includes a central sump area and a raised perimeter. The pad is usually larger than the truck so that any material spilling off the truck ends up in the central sump. The material is then kept in the sump until enough has accumulated to be removed and transported to a waste disposal site. Unfortunately, both the removal and disposal are expensive. Since the pads are usually uncovered, any precipitation that falls onto the pad also becomes contaminated by the materials present and must be disposed of at high cost as well. This precipitation problem has been solved with a transfer pad cover, as described in the inventor's U.S. Pat. Nos. 5,197,240 and 5,327,691.
However, there are two other significant problems with conventional transfer pads. First, it is relatively 30 difficult and expensive to create a concrete pad surface that will remain liquid-impervious for an extended period of time. The effects of constant truck traffic, in addition to the effects of inclement weather, especially the deep freezes of the Northern winters, can easily lead to cracking of the concrete. Costly inspection and maintenance programs are then needed to maintain the pads. Second, the purpose of the conventional transfer pad, which is to maintain the dangerous (and ignitable) materials in one contained area also leads to a fire hazard, in that if the accumulated material in the pad's sump is ignited, the truck is essentially sitting in a fire bath. The ignitable material is spread thin and fully exposed to the atmosphere, providing an excellent environment for quick, intense flames.
In view of these deficiencies, it is an object of the invention to provide a transfer pad that is permanently liquid impervious with no maintenance.
It is another object of the invention to provide a transfer pad that minimizes the fire hazards from spilled ignitable materials.
It is yet another object of the invention to provide a transfer pad that is easy and economical to manufacture and maintain.
It is a further object of the invention to provide a transfer pad that is easily monitored and easily drained of any spilled materials.